1. Field of the Invention
The present invention relates generally to a cushioning device disposed between two members, for damping or isolating vibrations applied thereto primarily in its axial direction, and more particularly to a technique for increased ease of assembling of a fluid-filled cushioning device for damping or isolating input vibrations, based on flows of a non-compressible fluid within the device.
2. Discussion of the Prior Art
Various types of fluid-filled cushioning devices have been recently proposed as a vibration damping/isolating mount or support disposed between two members of a vibration system. A cushioning device of these types is filled with a suitable non-compressible fluid, for damping and/or isolating input vibrations, in dependence on flows of the fluid through an orifice or restricted fluid passage formed in the device, or by utilizing an effect of inertia of the fluid mass.
An example of such a fluid-filled cushioning device is a strut bar cushion used in a vehicle suspension system, which is connected between a shaft member such as a strut bar, and a suitable support member such as a body of the vehicle, in order to damp or isolate mainly a vibrational load applied in its axial direction.
A commonly known fluid-filled cushioning device includes (a) an inner sleeve through which a suitable shaft member is inserted for attachment to the device, (b) a cylindrical elastic body mounted on an axially intermediate portion of the inner sleeve and provided at its outer circumferential portion with orifice-defining means which has an orifice formed therethrough, (c) a pair of annular elastic members each having an integrally formed inner retainer member and an integrally formed outer sleeve which are spaced apart from each other in an axial direction of the elastic members, the elastic members being mounted on the inner sleeve such that the inner retainer member is press-fitted in a corresponding one of opposite axial end portions of the inner sleeve while the orifice-defining means of the cylindrical elastic body is sandwiched by and between corresponding axial end faces of the outer sleeves of the annular elastic members, in the axial direction of the elastic members, and such that the inner sleeve, the cylindrical elastic body and the pair of annular elastic members cooperate with each other to define two fluid chambers which are filled with a suitable non-compressible fluid and which are separated from each other by the elastic body and communicate with each other through the orifice, and (d) a cylindrical bracket which is mounted on outer circumferential surfaces of the outer sleeves of the annular elastic members, and which is attached to a suitable support member.
In the thus constructed fluid-filled cushioning device, the mounting of the annular elastic members on the inner sleeve, and the mounting of the cylindrical bracket on the outer sleeves of the annular elastic members, are both conducted within a mass of the non-compressible fluid, so that the fluid chambers are filled with the fluid. The two outer sleeves of the annular elastic members are forced against each other in the opposite axial directions by the cylindrical bracket, so that fluid tightness of the fluid chambers is maintained.
In the known fluid-filled cushioning device constructed as described above, however, the mere mounting of the pair of annular elastic members on the inner sleeve does not establish fluid tightness of the fluid chambers which are defined in the intermediate assembly of the inner sleeve and the elastic members. Accordingly, the cylindrical bracket must be mounted on the outer sleeves of the annular elastic members, also within the fluid mass, following the mounting of the elastic members on the inner sleeve. This mounting of the cylindrical bracket is difficult, since the bracket should be subjected to an operation to urge the outer sleeves against each other within the fluid mass. Therefore, the assembling efficiency is comparatively low. Further, there may be left the fluid within spaces other than the fluid chambers, for instance, within a clearance between the outer surfaces of the outer sleeves and the inner surface of the cylindrical bracket. The fluid in such spaces may leak during installation or use of the cushioning device on the vehicle body, causing undesirable contamination of the device itself and the environment of the device.